Optical disk

ABSTRACT

An optical disk and an apparatus for recording/reproducing on the disk. The disk has extra tracks that are used for tracing by the pickup when the apparatus is started or remains in a pause mode longer than a predetermined time. The intensity of the light emitted by the pickup can be reduced while scanning the extra tracks.

This is a Division of application Ser. No. 07/069,084, filed July 2,1987 U.S. Pat. No. 4,817,068.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical disk and an optical diskapparatus in which information is optically recorded and reproduced on apredetermined recording layer on the disk.

2. Background of the Invention

Recently, optical disks have been developed and many of them have beencommercialized. The optical disks use metal, coloring matter, and thelike, in information recording layers and are capable of beingreproduced after recording has been made. However, the information whichhas been once recorded cannot be re-recorded or written over. In spiteof such an inconvenience, attention is particularly paid to the opticaldisks because the optical disks have a capacity relatively larger thanother recording media.

In a conventional optical disk apparatus, on the other hand, a pickup(that is, an information detecting point) is caused to repeatedly tracethe last track (a pause track) on which the recording/reproducingoperation was ended at the last time. As shown in FIG. 5, the pickuprepeatedly traces a spiral track with repeated track jumps in aso-called pause mode in which the information recording/reproducingoperation is temporarily interrupted (or in a wait state). If one andthe same pause track is thus repeatedly traced for a long time, however,there has been a risk of damage of recorded information on the pausetrack depending on the material of a recording layer even if theintensity of light is adjusted in advance to be small enough not tocause any substantial change in the recorded information in a normalreproducing operation.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to eliminate thedisadvantages in the prior art.

It is another object of the present invention to provide an optical diskapparatus in which a pickup traces predetermined tracks including tracksother than a pause track in a pause mode.

It is still another object of the present invention to provide anoptical disk apparatus in which a pickup traces a land between adjacenttracks in a pause mode.

In order to achieve the above objects, according to the presentinvention, in the optical disk provided with tracks formed in advance soas to be traced by a pickup, the tracks are grouped into those belongingto a first region to be traced by the pickup when information recordingand reproducing is performed, and those belonging to a second region tobe traced in a pause mode, substantially none of the information beingrecorded or reproduced on the tracks belonging in the second region.

That is, on the optical disk, the tracks are formed in advance so thatthe pickup produces a tracking error while tracing the tracks. Thetracks are grouped into those belonging to a first region to be tracedby the pickup when information recording and reproducing is performed,and those belonging to a second region to be traced in a pause mode.Substantially none of the information is recorded or reproduced on thetracks belonging in the second region.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will become apparentduring the following discussion of the accompanying drawings, wherein:

FIG. 1 is a block diagram showing an optical disk apparatus according tothe present invention;

FIG. 2 and 3 are flowcharts for explaining the operation of theapparatus;

FIG. 4 is a diagram for explaining the regions of the optical diskaccording to the present invention;

FIG. 5 is a diagram for explaining track jump.

FIG. 6 is a waveform diagram of a tracking error signal;

FIG. 7 is a flowchart for explaining the operation of the apparatus; and

FIGS. 8 and 9 are diagrams for explaining the relationship between thetrack and an information detecting beam spot.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Referring to the drawings, preferred embodiments of the presentinvention will be described hereunder.

FIG. 1 is a block diagram showing an optical disk apparatus according tothe present invention. An optical disk 1 is rotated at a predeterminedspeed by a spindle motor 2. The speed is controlled by a spindleservo-circuit 10. A pickup 3 includes a light source such as asemiconductor laser, or the like, so that light radiated from the lightsource is made to impinge onto the optical disk 1 to perform informationrecording and reproducing on the disk. The pickup 3 is provided with atracking actuator 4 for controlling the horizontal position of the lightso that the light can track a track and with a focus actuator 5 forfocusing the light on an information recording layer of the opticaldisk 1. The pickup 3 is moved by a linear actuator 6 relative to theoptical disk 1 in its radial direction. Servo-circuits 7, 8 and 9 areprovided for controlling respectively the tracking actuator 4, the focusactuator 5, and the linear actuator 6. Those servo-circuits 7 through 10are controlled by a sequence controller 11 to operate in accordance witha predetermined sequence. A main controller 12 is arranged to performpredetermined operations of the sequence in accordance with a programstored in ROM 13 to control the circuit and the other elements. Amodulation/demodulation circuit 14 is provided to demodulate areproduced signal from the pickup 3 or to modulate a recording signal ina predetermined manner so as to apply the modulated signal to the pickup3. An error-correction coding circuit 15 is arranged to correct anyerror in the reproduced signal or to add an error-correction code to therecording signal so as to output the recording signal with theerror-correction code. A RAM 16 stores the reproduced signal or therecording signal. The reproduced signal and the recording signal aretransferred mutually between a host controller 18 and the maincontroller 12 through an interface 17.

The operation at the start is performed, for example, in accordance withthe flowchart shown in FIG. 2. At first, in a command entry routine, themain controller 12 or the host controller 18 monitors whether or not anycommand is entered. When a command other than that instructing a startis entered, the routine is shifted to another command routine. When theentered command is that one instructing a start, an output is appliedsuccessively to the servo-circuit 10, the servo-circuit 8, and theservo-circuit 7 through the sequence controller 11 so that the spindlemotor 2 is rotated, a focus servo loop is turned on, and a trackingservo loop is turned on.

Next, an address where the pickup 3 is positioned is read out by thecontroller 12 or the controller 18 from a signal reproduced from theoptical disk 1 and processed by the modulation/demodulation circuit 14.When the readout address A is not between predetermined addresses A₁ andA₂, a control signal is applied to the servo-circuit 9 or to the servocircuit 7 to search the address A₁. That is, the position of the pickup3 is moved to the position of the address A₁. When the address A of thepickup 3 assumes the value A₁ (between the values A₁ and A₂), thetracking servo loop which has been turned off in the search operation isturned on again and the pickup 3 traces (reproduces) the tracks from theaddress A₁ to the address A₂. When the pickup 3 reaches the track of theaddress A₂, the track with the address A₁ is searched again. When thetrack is searched, the tracking operation of the pickup 3 is repeated toreach the track at the address A₂. In a pause mode in which the pickup 3thus repeatedly traces on the tracks between the addresses A₁ and A₂,the state of the command entry routine is monitored so that when anycommand is entered, the operation is shifted to the routine of theentered command.

In writing or reading, the operation is carried out in accordance withthe flowchart as shown in FIG. 3. That is, when a writing or readingcommand is entered, the writing or reading operation is executed inresponse to the command. When the writing or reading operation iscompleted, the pickup jumps back to the one track of the last address(pause track) and this track is repeatedly traced. At that time, a timeris started and, if another command is entered within a predeterminedtime T₁, the operation is shifted to the routine of the entered command.When no command is entered within the predetermined time T₁, the pickup3 is moved to predetermined region, i.e., a home position on theinnermost circumference. The pickup 3 remains in a pause state byrepeatedly tracing the track with an address A₀ in the home position onthe innermost circumferences so as to wait for the entry of the nextcommand. Alternatively, the pickup 3 may be caused to trace not onetrack of the address A₀ but a plurality of tracks from an address A₀₁ toan address A.sub. 02 within the region of home position.

Further, the pickup 3 may be caused to trace not the track in the homeposition but tracks between the predetermined addresses A₁ and A₂ withinan arbitrarily set region similarly to the case described above, or maybe caused to trace not the track of a preset address but a plurality oftracks N in number in the vicinity of the pause track upon terminationof carrying out of the last command.

Of course, in the start operation, the pickup 3 may be caused to tracetracks N in number in the home position or in the starting position.

Thus, in the starting operation, or in the pause mode in thewriting/reading operation, the pickup is caused to trace thetrack/tracks other than the pause track upon termination of the lastcommand execution, so that the recorded information in the pause trackcan be prevented from being damaged.

As shown in FIG. 4, assume that track regions B, C and D to be traced bythe pickup 3 are formed between a non-track region. A in the innermostcircumference and another non-track region E in the outermostcircumference. The tracks, for example, in the region B are then usedfor a producer of the optical disk 1 to record necessary information.Further, the tracks in the region D are used for a user to recorddesired information. The tracks in the intermediate region C can be madeto be the tracks of the above-mentioned home address A₀ (or multipleaddresses A₀₁ through A₀₂), that is, to be the tracks for the exclusiveuse of the pause. Of course, the region B for the producer and theregion C for the pause may be reversed in positional relation to eachother. Because substantially no information is recorded on the tracks inthe region C for the exclusive use of the pause, the region C can bemade of a material different from that of the regions B and D, that is,can be made of a material which is hardly changed in quantity as well asin shape even if the material is irradiated with light for a long time.

Because the tracks of the addresses A₁ through A₂ are established in theregion D, it is preferable to make the region D relatively wide.

Further, in the pause mode, the intensity of light may be made weaker orsmaller (including zero, that is, to be off) than that in the normalinformation-reproducing operation. The control of the light intensitycan be implemented by, for example, changing the level of the voltageapplied to a laser diode from a high level to a low level or vice versa.Therefore, when the servo, for example, for the focusing-servo,tracking-servo, or the like, becomes difficult, the gain of the servocan be made larger in the pause mode than that in the normal reproducingoperation. In this regard, an advantageous effect can be obtained suchthat the intensity of light can be made weaker. Further advantageouseffect can be obtained if in the pause mode the pickup traces particulartracks in a manner described above while reducing the intensity oflight.

As described above, according to the present invention, in an opticaldisk provided with tracks formed in advance so as to be traced by apickup, the tracks are grouped into those belonging to a first region tobe traced by the pickup when information recording/reproducing isperformed, and those belonging to a second region to be traced in apause mode, substantially no information being recorded/reproduced onthe tracks belonging in the second region. Accordingly, the recordedinformation can be prevented from being damaged even if the optical diskis irradiated with the light continuously for a long time in the pausemode.

Another embodiment of the present invention will next be described. Inthis embodiment, the pickup traces a land between adjacent tracks in apause mode.

In a recording/reproducing mode, assume that the tracking error signalis such that the level increases in the direction of positive polaritywhen the pickup 3 moves toward the innermost circumference of theoptical disk 1 (i.e., in the left direction in the FIG. 6) and that thelevel increases in the direction of negative polarity when the pickup 3moves toward the outermost circumference of the optical disk 1 (i.e., inthe right direction in the FIG. 6), as shown by a solid line in FIG. 6.During the movement of the pickup toward the innermost circumference ofthe disk 1, if the apparatus is put in the pause mode, the polarity ofthe tracking error signal will be reversed as shown by a dotted line inFIG. 6, since in the pause mode, the pickup is jumped back toward theoutermost circumference to keep tracing the same track. As a result, thetracking servo loop operates the pickup so that it traces a land L₁between two adjacent tracks T₁ and T₂ , assuming that the apparatus isput in the pause mode when the track T₁ is being traced. Whether thepickup traces a land L₀ at the inner circumference side of the track T₁or the land L₁ at the outer circumference side of the track T₁ dependsupon the position of the pickup. In order that the outer (or inner)circumference side land may always be traced under any circumstance, ajump pulse may be generated by the tracking servo circuit at the timeimmediately before or after the polarity of the tracking error signal ischanged.

In the pause mode, the pickup operated to jump back by one track as theoptical disk rotates for one revolution. During this pause modeoperation, the pickup repeatedly traces the land L₁ adjacent the pausetrack T₁, so that even if the pause mode operation continues for a longperiod of time, the track T₁ would not be damaged.

When the pause mode is ended, the polarity of the tracking error signalreturns to the original state, and the pickup again start tracing thetrack T₁. At this time, a jump pulse may be produced so that the pickupalways moves to the direction of the track T₁. Even if the pickup movesto the opposite direction, i.e., to the direction of track T₂, thepickup may be controlled so as to return to the track T₁ by reading theaddress of the currently tracing track. Access time for doing so is notso long.

The above-described operation is illustrated by the flowchart shown inFIG. 7.

FIG. 8 is a diagram illustrating a portion of the optical disk wheretracks or grooves and lands are formed in consecutive manner on theoptical disk. The present invention is applicable not only to the diskshown in FIG. 8 but also to the optical disk of the sample servo type asshown in FIG. 9. In the case of sample servo type, a tracking errorsignal is produced from the level difference of RF signals obtained fromtwo warbled pits w₁₁ and w₁₂ which are positioned in staggered fashionwith respect to track T₁ (imaginary track). The tracking error signalthus produced is held until the pickup is moved to the subsequentwarbled pit position. Accordingly, in the pause mode, the tracking errorsignal may be produced from the level difference of the RF signalobtained at the position of warbled pit w₁₂ for the track T₁ and theposition of warbled pit w₂₁ for the adjacent track T₂. In CAV (ConstantAngular Velocity) disks, the positions of warbled pits are aligned alongthe radius of the disk, the timing signals need not be changed so as tocorrespond to the position of the warbled pit.

It is possible to position the pickup between the tracks by adding anoffset to the tracking error signal. Although it is difficult toprecisely control the position of the pickup between the tracks, thepickup can roughly be positoned between the tracks.

It is further possible for the pickup to consecutively trace a pluralityof tracks within a predetermined region in lieu of tracing a signal landrepeatedly.

While it has been described the case where the input means (not shown)inputs a pause mode, the similar operation can be performed for the casewhere the pause mode is automatically set after termination of recordingoperation.

The present invention is also applicable to the recording/reproducingapparatus for a recording medium other than the optical disk.

According to the second embodiment of the present invention, it isadvantageous in that the track from which the recorded informaiton isreproduced and the information recorded on the disk can be preventedfrom being damaged.

What is claimed is:
 1. An optical disk, comprising a plurality ofoptical information tracks recorded thereon for tracing by a pickup,said tracks being divided into:a first group of tracks in a first regionof said disk containing information to be reproduced with said pickup;and a second group of tracks in a second region of said disk for tracingby said pickup during a pause mode and being blank, containing none ofsaid information to be reproduced with said pickup except addressinformation identifying said second group of tracks for the exclusiveuse of the pause mode and for no other purpose.
 2. An optical diskincluding a plurality of optical tracks thereon for tracing by a pickupof an optical disk apparatus having a pause mode, said tracks beingdivided into at least two groups, a first group of said tracks, all ofwhich are in a first region of said disk, containing information to bereproduced by said pickup, and a second group of said tracks, all ofwhich are in a second region of said disk different from said firstregion, dedicated exclusively to the pause mode of said optical diskapparatus and blank containing no information to be reproduced by saidpickup except address codes identifying said second group of said tracksfor the exclusive use of the pause mode and for no other purpose.
 3. Anoptical disk as claimed in claim 2, further including a third group oftracks, all of which are in a third region of said disk, said secondregion being situated between the first and third regions, said thirdgroup of tracks containing information to be reproduced by said pickup.4. An optical disk as claimed in claim 2 wherein the disk physicalmaterial in the first region is different from the disk physicalmaterial in the second region.
 5. An optical disk as claimed in claim 3,wherein said first group of tracks contains information to be reproducedto the user of the optical disk and said third group of tracks containscontrol information for use by said optical disk apparatus in itscontrol of the playback of said optical disk.